Over the years, numerous techniques for charge/electric field/voltage detection and measurements have been developed. One of the biggest challenges for designers of such instrumentation is to devise ways of preventing the exchange of the electric charges between the measured object and the meter. This is especially important for the objects under test for which the amount of charge is limited, and where the presence of the measuring instrument affects the physical state of that object. In such cases the input impedance of the meter has to be as high as possible, and one of the ways to achieve that is by avoiding any physical contact with the measured object.
Non-contacting instruments are widely available, but many have drawbacks. Meters such as those utilizing Kerr or Pockels effect, rotating vane fieldmeters, fieldmeters with mechanically actuated sensors or the like generally lack precision. Other meters such as electrostatic voltmeters (ESVMs), which also rely on mechanical excitation of the sensors (tuning fork or a precision piezoelectric or acoustic drive) are relatively expensive and complicated. Recently developed micro-electromechanical devices (MEMS) introduce a new class of miniature fieldmeters, but fabrication of field sensing MEMS appears to be a complicated and not easily-repeatable process. Other types of electric-field meters such as capacitive coupling or induction instruments rely on variation of the electric quantity that is being measured; and therefore, they are not useful for detection and quantification of static (DC) electric charges and fields.